Dental biofilm is an important factor in periodontal health and disease (review: Socransky and Haffajee 2002), and is a more correct wording for the term plaque. Most biofilms are biologically compatible with health, as their formation is influenced by the selective pressure of the host organism. It is also of great practical interest that bacteria organized in biofilms are highly resistant to antibiotics as compared to those in a planktonic state. In the development of dental biofilms, the host receives bacteria with different properties from close relatives and others, depending on the living conditions (Tinoco et al 1998). If there are pathogenic bacteria among these, the possibility for developing periodontitis increases (Preus et al 1995). This indicates that periodontal treatment must be aimed at breaking the ecology of the pathogenic biofilm, and then increase the organisms' ability to perform its selective pressure, following treatment, in the making of a new biofilm low of, or free from pathogenic microorganisms.